Making Sense of Prescription Maps for Variable Rate Irrigation
Variable rate irrigation (VRI) involves applying different amounts of water to different areas of the field, writes Guy Sela at PrecisionAg. This innovative technology has many advantages. It allows farmers to:
- Maximize yields
- Save water
- Avoid or minimize nutrient leaching
- Avoid or minimize runoff
- Save energy
Agricultural fields never are uniform. Variability may be related to the soil or the crop itself. Soil is heterogenous and there will always be variability in soil properties throughout the field. Spatial variability in topography and soil texture greatly affect the water availability for the crop.
Soil texture may vary horizontally as well as throughout the soil profile. Soils of different textures retain different amounts of water and, therefore, will require different irrigation rates and scheduling. Sandy soils require more attention, as they can store only a small amount of water. Therefore, they must be irrigated more frequently and with smaller amounts of water in each irrigation. Too high irrigation depth in a sandy soil may result in water waste and leaching of nitrogen below the root zone of the crop.
On the other hand, heavy-textured soils can store more water and, therefore, must be irrigated at larger intervals and with greater amounts of water.
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